Protection of buildings or weirs against hollowing out or washing away



K. TERZAGHI PROTECTION OF BUILDINGS OR WEIRS AGAINST HOLLOWING OUT OR WASHING AWAY Filed July 17. 15923 5 .M ii

Patented duly l, 1194.

KARL TERZAGHI, OF VIENNA, AUSTRIA.

PROTECTION OF BUILDINGS OR WEIRS -AGAIN ST HOLLOWING OUT OR WASHING AWAY.

Application filed July 17, 1923. Serial No. 652,175.

To all whom it may. concern:

Be it known that I, Dr. KARL TERZAGHI, a citizen of the Republic of Czechoslovakia residing at Vienna, Austria, have invented certain" new and useful Improvements in Protection of Buildings or Weirs Against Hollowing Out or Vvas hing Away, of which the following is a specification;

This invention relates to means which will prevent the hollowing out orwashing away of buildings, retaining walls, weirs and the like by that part of thebackwater which leaks or trickles through the foundation. The characteristic feature of the invention consists in arranging either at the bottom of the building or weir. facing the air or underneath the foundation of the building or the like a filter of such a character, that it will permit the free outflow of 2 the underground-water but prevent the passing through of constituents or parts of the soil, and whereby the filter is loaded or weighted in such a manner, that the layers located underneath the filter and throu h which the leakage water flows cannot e driven upwardl If desired these layers may be loaded by the weight of the filter only.

The drawing illustrates by way of example several modes of carrying out the present invention.

Figs. 1, 2, 3 and 4 are sections through weirs provided with various arrangements for preventing hollowing out or washing away.

Figs. 5 and 6 are sections through modified constructions of weirs over whose tops 1 or crowns the water is flowing.

The arrangement according to Fig.1 comprises a weir 8, provided at the bottom end of its outside or of its side facing the air with a layer 7" permeable to water and consisting for instance of grit, gravel and broken stones. The said layer 7 is loaded or weighted by a berm t and on its outside face there is arranged a collecting channel g by which the water coming from the filter is led away. The cross-sectional areaof the berm is determined by a static calculation in such a manner, that the forces, produced underneath the berm by the stream of the underground-water and directed upwardly, are balanced by the weight of the berm. The correctness of the tic calculation on required weight of the berm for holdingdown the raisingconstituents or parts of the soil is effected by the stiffness or rigidity against flexure or. bending of a cantilever construction p, dimensioned for pressure from underneath. The filter required for permitting the free outflow of the underground-water is disposed between the cantilever construction p, and the soil, the leakage water being collected in and flowing ofi through the channel g.

In the construction illustrated in Fig. 3, the weight required for holding down the raising parts of the soil 0 is formed by the weight of the weir, the leakage water passing from the filter f into the channel g.

In the construction according to Fig. 4 also the weight of the water W at the weir is utilized for loading or weighting the filter f.

In such cases in which the water flows over the stop or crown of the weir (Fig. 5)

it ismecessary to prevent a silting of the filter by the sand and mud or loam carried at high water. This object may be attained by covering the filter with a protecting sill of known construction, whereby openings or passages are provided in the protecting sill for leading the leakage water into the underground-water. These openings or passages are of such a cross-sectional area, that the velocity of the entering leakage water will be sufficiently great to' prevent the choking of the said openings. In many cases this is obtained by making the open ings nozzle-shaped and directing them down-stream.

In the construction illustrated in Fig. 6 the forces directed upw'ardly by the stream of the underground-water are balanced or absorbed by forming the protecting sill as a cantilever and strengthening it against the upwardly actingpressure; the exit of the leakage water taking place through an opening of the same construction as has been contact with bodies or parts (brickwork, sheet-pilings, pile-plankings and so forth) which are inpermeable to water and this part solely reduces the amount of the leakage water to the desired extent by lengthening the path of leakage. However, this part of the foundation does not constitute a feature of the invention. At the second part of the foundation the soil is covered by a filter which essentially is more permeable to water than the soil. At the boundary between the first and the second part the outflow velocity of the leakage water is at a maximum and at that place or zone the leakage water has the tendency to raise or drive u and wash away the soil. In order to prevent this procedure which imperils the building or weir the filter which is permeable to water is held down by the before described arrangements. Therefore the essential feature of the invention consists in directing the outflow of the leakage water to a place, where the upwardly directed forces produced by the fiow of the leakage water may becompensated in a simple and inexpensive manner by suit-ably loading or weighting the filter.

I claim 1. In means for preventing washing out of dam footing, a water retaining dam like structure, and a water permeable filter bed extending at the lower part of said structure and formed of gravel like material, a substantial part of said filter bed being on the side opposite that on which the retained water presses.

2. In means for preventing washing out of a dam footing, a water retaining dam like structure, a water permeable filter bed extending at the lower part of said structure and formed of gravel like material, a substantial part of said filter 'bed being on the side opposite that on which the retained Water presses, and means pressing on the top of said filter bed to retain it in place.

3. In means for preventing washing out of dam footing, a water retaining dam like structure, a water permeable filter bed extending at the lower part of said structure and formed of gravel like material, a substantial part of said filter bed being on the side opposite that on which the retained water presses, means pressing on the top of said filter bed to retain it in place, and having outflow means leading upwardly there through.

4. In means for preventing washing out of dam footing, a water retaining dam like structure, and a water permeable filter bed disposed beneath said structure and having a substantial part thereof on the side opposits that on which the water presses.

5. In means for preventing washing out of dam footing, a water retaining dam like structure, a water permeable filter bed disposed beneath said structure and having a substantial part thereof on the side opposite that on which the water presses, and means bearing on top of the projecting portion of the filter bed to retain it in place.

6. In means for preventing washing out of dam footing, a water retaining dam like structure, a water permeable filter bed disposed beneath said structure and having a substantial part thereof on the side opposite that on which the water presses, means bearing on top of the projecting portion of the filter bed to retain it in place, and having outflow passages leading upwardly therethrough.

In testimony whereof I afiix my signature.

DR. KARL TERZAGHI.

Witnesses:

VICTOR GUY, RUDOLPH THEUMER. 

